# mcrypt_create_iv

(PHP 4, PHP 5, PHP 7 < 7.2.0, PECL mcrypt >= 1.0.0)

mcrypt_create_iv — Creates an initialization vector (IV) from a random source

Warnung

Diese Funktion wurde in PHP 7.1.0 als DEPRECATED (veraltet) markiert und in PHP 7.2.0 REMOVED (entfernt).

Alternativ können die folgenden Funktionen verwendet werden:

- random_bytes()

### Beschreibung

mcrypt_create_iv(int `$size`, int `$source` = MCRYPT_DEV_URANDOM): string

Creates an initialization vector (IV) from a random source.

The IV is only meant to give an alternative seed to the encryption routines. This IV does not need to be secret at all, though it can be desirable. You even can send it along with your ciphertext without losing security.

### Parameter-Liste

`size`
  The size of the IV.
`source`
  The source of the IV. The source can be `MCRYPT_RAND` (system random number generator), `MCRYPT_DEV_RANDOM` (read data from /dev/random) and `MCRYPT_DEV_URANDOM` (read data from /dev/urandom). Prior to 5.3.0, `MCRYPT_RAND` was the only one supported on Windows. Note that the default value of this parameter was `MCRYPT_DEV_RANDOM` prior to PHP 5.6.0.

  > Hinweis: Note that `MCRYPT_DEV_RANDOM` may block until more entropy is available.

### Rückgabewerte

Returns the initialization vector, or `false` on error.

### Beispiele

Beispiel #1 mcrypt_create_iv() Example

`<?php
$size = mcrypt_get_iv_size(MCRYPT_CAST_256, MCRYPT_MODE_CFB);
$iv = mcrypt_create_iv($size, MCRYPT_DEV_RANDOM);
?>`

### Siehe auch

- » http://www.ciphersbyritter.com/GLOSSARY.HTM#IV
- » http://www.quadibloc.com/crypto/co0409.htm
- Chapter 9.3 of Applied Cryptography by Schneier (ISBN 0-471-11709-9)
- random_bytes() - Get cryptographically secure random bytes

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